Perchlorato Complexes of Iridium and Rhodium

Submitted by J. PEONE, JR., t BRENDAN R. FLYNN, and L. VASKA Checked by W. H. BADDLEYJ and D. S. HAMILTON  

Tetrahedral perchlorate ion, [C104] , is an uncommon ligand.1 The molecular perchlorato complexes of iridium and rhodium2 described here are thus of inherent interest as such, but their principal importance lies in their versatile reactivity. These compounds undergo addition, substitution, and addition-substitution reactions with many molecules and ions.3 In particular, the latter conversions lead to a remarkable number of cationic d8 complexes of these metals, which offer themselves as a unique series for a study of the electronic properties of a variety of molecules as ligands (L).3 Not less significant are the substitution reactions in which the perchlorate ligand is replaced by other unusual anions.4 

The present preparative procedure for perchlorato complexes of rhodium and iridium appears to be of general utility for the synthesis of perchlorato complexes of transition metals. The assignment of trans planar structures for [M(OC103)(CO)(Ph3P)2] (M = Ir, Rh) is based on the vibrational and electronic spectral similarities between the perchlorato complexes and their well-known chloro precursors, tims-[MCl(CO)(Ph3P)2].5,6 

The final benzene-hexane filtrate still contains some dissolved rrans-[Ir(OC103)(CO)Ph3P)2]. On addition of triphenylphosphine (10 g., 39 mmoles) to this solution, an orange precipitate of the ionic perchlorate, [Ir(CO)(Ph3P)3] [C104],2 is obtained which is collected and treated as above yield, 0.70 g. (17%). This procedure thus affords a nearly quantitative (99 %) recovery of the total iridium used. 

The yellow frans-carbonylperchloratobis(triphenylphosphine) iridium(I) is a crystalline solid which slowly decomposes on standing in air. It must be stored in an inert atmosphere (N2, Ar) or in vacuo, but even under these conditions the complex deteriorates within several weeks. For studies of its properties and reactions, freshly prepared samples should be used. The compound is insoluble in water and hexane, and soluble in chloroform, benzene, ethanol, acetone, methanol, nitromethane, and chlorobenzene. In the latter four solvents, the molar conductances AM of (2-5) x 10 4 M solutions at 25° are 160, 110, 77, and 0.7 Q-1, respectively, which shows that a solvolytic ionization occurs in polar solvents.2 

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